Slack Technologies, a corporate messaging and collaboration software startup, has received inquiries about a potential takeover from technology companies including Amazon, according to a report on Thursday.

Slack is a platform where employees can send messages, collaborate, organize and share files. The technology also integrates with a wide variety of business software — such as Salesforce.com and Microsoft’s Skype — so employees can do all their work within Slack.

San Francisco-based Slack has raised more than $500 million from venture capitalists and was valued at $3.8 billion at its last private financing round a year ago.

Both Amazon and Slack were not immediately available to comment outside of regular US business hours.